Ultrasonic transducers, and in particular, phased array ultrasonic transducers, are frequently utilized for a variety of medical applications. In one such application, the transducer is disposed at the end of an endoscope which is suitably positioned in the patient's esophagus for scanning such internal organs as the heart. When used in this manner, this transducer or probe is referred to as a transesophageal probe, and the procedure is referred to as transesophageal echocardiography (TEE) when the probe is utilized for scanning the heart. Other invasive probes which have similar structures and requirements include transrectal, transnasal and transvaginal probes.
The shaft of the endoscope serves as an enclosure for electrical and mechanical cables which couple the transducer and other electrical components of the endoscope to an external power source and external controls. Since a probe of this type and its shaft is positioned inside the body, the probe and shaft must be sealed to protect them against attack from body fluids and acids, as well as against sterilizing solutions and cleaning solutions either inside or outside the body. Moreover, the probe and shaft must protect the patient from currents carried by the electrical cables. Thus, the transducer, as well as the shaft of the endoscope must be enclosed within an insulative protective outer covering. Such a covering also protects the body from irritation as result of probe rotation.
Existing shafts of such transesophageal probes typically comprise an inner, convoluted metal core which provides the required crush resistance to the shaft, a stainless steel braided sheath which is constructed over this inner core, and an outer coating of an elastomeric material. The elastomeric material serves as an insulator to protect the patient from electric currents, as a smooth, corrosion resistant surface to facilitate the placement of the probe and as a cover to protect the mechanical and electrical components of the endoscope from damage by bodily fluids.
One of the major causes of failure of this type of probe shaft is the physical penetration of this outer elastomeric coating by the patient, for example as a result of the teeth of the patient being clamped tightly about the shaft or as a result of the shaft being rubbed against the patient's teeth during insertion of the probe. Even with the most cut-through resistant, flexible coatings available, such as urethanes, eventually the coating is penetrated by the patient's teeth, or by wear and tear from other sources. These penetrations are exacerbated by exposure to stomach acid, cold sterilants and cleaning fluids commonly used in a clinical setting. Once the elastomeric coating is penetrated, there is a direct, electrically conductive path between the patient and the probe, thereby introducing a potential safety risk to the patient. Even a single small penetration of the outer elastomeric coating can provide a direct electrical path to the patient, once the probe has been inserted into the esophagus.
It is therefore an object of the present invention to provide a shaft for an invasive body probe which is resistant to penetration therethrough to the interior core during normal use.
It is another object of the present invention to provide a shaft for an invasive body probe which electrically insulates the patient from the conductive metal portion of the shaft, even if the outer coating is penetrated.
It is another further object of the present invention to provide a shaft for an invasive body probe which adequately protects the shaft from damage caused by the patient during normal use.
It is yet another further object of the present invention to provide a flexible, hollow shaft for use in a transesophageal probe which provides an enclosure for electrical and mechanical cables, and which adequately protects the cables and the patient from damage resulting by penetration of the shaft coating by the patient during use.